I never thought about the intake manifold gasket. I'll look into that after I am certain it's not IACV related. And I've thoroughly cleaned the throttle body already so I'm pretty sure that isn't the issue. If getting a new IACV gasket doesn't solve the problem then I'll pick up a few extra throttle body and IACV gaskets and start switching parts between my two cars until I figure out which part is causing the problem.
Could be the fuel injectors. Take a listen while it is running with a long screw driver pressed up against the base of each injector and the round handle end in your ear. You can hear whether or not the fuel injector is clicking and if it is clicking regularly. Might also be the distributor. You could swap distributors...
Hmm that's a new one I'll have to try that once I eliminate the possibility of a bad IACV or throttle body. I replaced the gasket on the IACV today, but it still has a vacuum leak. I'm thinking its probably the throttle body gasket that's leaking now because I've had it apart at least half a dozen times and its not sitting very flat anymore.
I swapped both the IACV and the throttle body with the old car and it solved the vacuum leak, but now I'm back where I started. It still idles rough when its idling around 750 RPM. I was watching the fuel trims as I took it for a drive and I noticed its running rich when idling and runs lean when accelerating but not WOT. Its like it goes from too much fuel to not enough fuel as I push the gas pedal.
What I don't understand is how a vacuum leak can cause it to run rich at idle. A vacuum leak would cause extra air to get in which would lean it out wouldn't it?
I checked the O2 sensor readings using my phone connected to the car's OBDII port and at idle it will hang out at 0.04 volts for a while then jump up to 0.8 volts for a while then back to 0.04 volts. does this sound normal? At some point I want to swap the front O2 sensors between my accords and see if that makes a difference. Also does anyone know where the long coolant line that connects to the IACV goes because I need to replace it on my old sedan. The only way I was able to get the IACV off was to cut the hose. Also how long is it and what size is it?